The water supply to Crimea was cut off after Russia stole it from Ukraine. And why should Ukraine send water to the thieving Russian scum?
https://www.eurasiareview.com/16042020-the-water-crisis-in-crimea-analysis/
It wasn't the Ukrainians water to dam. For every right they claim against someone else, the same can be done to them.
If all that was required was claiming water, the sun would never set on the British Empire.